Adjustable ground speed and acceleration control devices, systems, and methods for walk-behind equipment

ABSTRACT

The present subject matter relates to adjustable ground speed control devices, systems, and methods for walk-behind equipment. A variable speed control system may include a control system base, a control lever selectively movable with respect to the control system base between a first operating position and a second operating position, a mode actuator positioned on the control system base for toggling between a standard mode and a selection mode, and an adjustment actuator positioned on the control system base in communication with a control unit to toggle between a first control mode and a second control mode when the mode actuator is in selection mode. The control unit applies a first acceleration profile to accelerate from the minimum operating speed to the variable maximum operating speed when in the first control mode and a second acceleration profile when in the second control mode.

TECHNICAL FIELD

The subject matter disclosed herein relates generally to variablecontrol systems for powered equipment. More particularly, the subjectmatter disclosed herein relates to variable speed and accelerationcontrols and methods for walk-behind working machines, such aslawnmowers.

BACKGROUND

Many walk-behind working machines, such as lawnmowers and other similarsmall powered equipment, have a self-propel system that propels ordrives the working machine at a selected ground speed. In such systems,a control system is typically carried on the handle to allow theoperator to engage and disengage the self-propel system and to select adesired ground speed. For example, many such control systems use apivotable ground speed control bail on the handle of the workingmachine. Generally, self-propelled drive systems can be divided into twocategories: single/multiple speed, and variable speed. Insingle/multiple speed drive systems, the ground speed is fixed by one ormore gear ratios, and it can only be adjusted by selecting a differentgearset (if available). In contrast, variable speed drive systems allowthe operator the ability to “infinitely” adjust the ground speed of thelawn mower, such as by a slipping belt system where the belt tension isvaried, a slipping clutch system where the clutch pressure is varied, ahydrostatic transmission where a swash plate angle is variable, or anelectric drive system where the electric power supply is switched.

Even in such variable speed drive systems, however, the maximumoperating speed is either fixed or, if variable, cumbersome to changewhile the working machine is being operated. Specifically, in allcurrently available adjustable control drive systems, the maximum speedsetting is made by a mechanical lever, rotary knob, or mechanicallatching device. In such configurations, an operator must remove atleast one of his hands from the control handle to make any adjustmentsto the maximum operating speed. Accordingly, making such adjustments canresult in the operator at least partially losing some degree of controlover the working machine. In view of these issues, it would be desirablefor a ground speed control system to allow for adjustment of the maximumspeed setting of the working machine without diminishing the operator'sability to control the working machine. It would also be desirable for aground speed control system to allow for adjustment of the rate ofacceleration of the working machine to enhance the operator's ability tocontrol the working machine. With current systems, either theacceleration is fixed, or the acceleration rate must be controlled bythe user when engaging the drive system by engaging the lever more orless slowly. Acceleration that is too quick can cause damage to grass byspinning the drive wheels. Acceleration that is too slow can befrustrating to the user and viewed as poor performance. The idealacceleration rate depends on each user's preference and the conditionsin which the user is operating the working machine.

SUMMARY

In accordance with this disclosure, adjustable ground speed controldevices, systems, and methods for walk-behind equipment are provided. Inone aspect, a variable speed control system for a walk-behind workingmachine is provided. The variable speed control system may include acontrol system base, a control lever selectively movable with respect tothe control system base between a first operating position and a secondoperating position, a mode actuator positioned on the control systembase for toggling between a standard mode and a selection mode, and anadjustment actuator positioned on the control system base incommunication with a control unit to toggle between a first control modeand a second control mode when the mode actuator is in selection mode.The control unit may be in communication with the control lever, theadjustment actuator, the mode actuator, and a machine component. Thecontrol unit selectively controls the operation of the machine componentbetween a minimum operating speed and a variable maximum operatingspeed. The control lever communicates with the control unit to controlthe machine component to operate at the minimum operating speed when thecontrol lever is in the first operating position and to control themachine component to operate at the variable maximum operating speedwhen the control lever is in the second operating position. The controlunit applies a first acceleration profile to accelerate from the minimumoperating speed to the variable maximum operating speed when in thefirst control mode, and wherein the control unit applies a secondacceleration profile to accelerate from the minimum operating speed tothe variable maximum operating speed when in the second control mode.

In another aspect, a variable speed control system for a walk-behindworking machine is provided. The variable speed control system for awalk-behind working machine may include a control system base, a controllever selectively movable with respect to the control system basebetween a first operating position and a second operating position, amode actuator positioned on the control system base for toggling betweena standard mode and a selection mode, and an adjustment actuatorpositioned on the control system base in communication with a controlunit to select an acceleration scale factor when in selection mode. Thecontrol unit may be in communication with the control lever, theadjustment actuator, the mode actuator, and a machine component. Thecontrol unit selectively controls the operation of the machine componentbetween a minimum operating speed and a variable maximum operatingspeed. The control lever communicates with the control unit to controlthe machine component to operate at the minimum operating speed when thecontrol lever is in the first operating position and to control themachine component to operate at the variable maximum operating speedwhen the control lever is in the second operating position. The controlunit applies the acceleration scale factor to control acceleration fromthe minimum operating speed to the variable maximum operating speed.

In yet another aspect, a method for varying a speed of a walk-behindworking machine is provided. A method for varying a speed of awalk-behind working machine may include the steps of actuating a modeactuator positioned on a control system base to select a selection mode,actuating an adjustment actuator positioned on the control system baseto select a mode for controlling a rate of acceleration of saidwalk-behind working machine from a minimum operating speed to a variablemaximum operating speed, moving a control lever with respect to acontrol system base between a first operating position and a secondoperating position, and without releasing the control lever, selectivelyactuating the adjustment actuator. Moving the control lever to the firstoperating position controls a machine component to operate at theminimum operating speed. Moving the control lever to the secondoperating position controls the machine component to operate at thevariable maximum operating speed. Actuating the adjustment actuatorincreases the value of the variable maximum operating speed.

Although some of the aspects of the subject matter disclosed herein havebeen stated hereinabove, and which are achieved in whole or in part bythe presently disclosed subject matter, other aspects will becomeevident as the description proceeds when taken in connection with theaccompanying drawings as best described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present subject matter will be morereadily understood from the following detailed description which shouldbe read in conjunction with the accompanying drawings that are givenmerely by way of explanatory and non-limiting example, and in which:

FIG. 1A is a perspective view of a variable speed control system in afirst operating position according to an embodiment of the presentlydisclosed subject matter;

FIG. 1B is a perspective view of a variable speed control system in asecond operating position according to an embodiment of the presentlydisclosed subject matter;

FIG. 2 is a schematic representation of a drive system for aself-propelled machine according to an embodiment of thepresently-disclosed subject matter;

FIG. 3 is a block diagram illustrating a system for adjusting a maximumoperating speed of a self-propelled machine according to one aspect ofthe subject matter described herein;

FIG. 4 is a front view of a variable speed control system according toan embodiment of the presently disclosed subject matter;

FIG. 5 is a front view of a variable speed control system according toanother embodiment of the presently disclosed subject matter;

FIG. 6A is a schematic view of a LED screen in standard mode;

FIG. 6B is a schematic view of a LED screen in selection mode;

FIG. 6C is a schematic view of a LED screen in traction control mode;

FIG. 7A is a schematic view of a lookup table according to an embodimentof the presently disclosed subject matter;

FIG. 7B is a graphical representation of standard and traction controlmodes according to an embodiment of the presently disclosed subjectmatter; and,

FIG. 8 is a flowchart illustrating yet another embodiment of thepresently disclosed subject matter.

DETAILED DESCRIPTION

The present subject matter provides variable speed control systems andmethods for walk-behind working machines, such as lawnmowers and similarpowered machines. In one aspect, the present subject matter providesvariable speed control systems and methods that can vary speed,comfortably hold a fixed speed, and vary the maximum speed at which theworking machine is operated.

Specifically, for instance, as shown in FIGS. 1a through 2, a variablespeed control system, generally designated 100 can comprise a handle 110configured to be gripped by an operator to control the operation of aworking machine, such as a lawnmower or other small powered machine, towhich handle 110 is connected. A control system base 120 can be attachedto or otherwise positioned near handle 110. A display 122 can beprovided on control system base 120 to provide warnings or otherindications of the operating state of the working machine, and an engineengagement control 124 (e.g., a push-button starter). A pair of controllevers, generally designated 130 a and 130 b, can be movably attached tocontrol system base 120. With this general configuration, control levers130 a and 130 b can be moved to control operation of a machinecomponent, such as for example a variable transmission for a self-propelsystem of the working machine.

In particular, a first control lever 130 a can comprise a first leverarm 132 a having a first end that is pivotably attached to controlsystem base 120 (e.g., about a pivot axis that extends through controlsystem base 120) and a second end substantially opposing the first endthat comprises a first grip portion 134 a. Likewise, a second controllever 130 b can comprise a second lever arm 132 b having a first endthat is pivotably attached to control system base 120 and a second endsubstantially opposing the first end that comprises a second gripportion 134 b. Specifically, for example, as shown in FIGS. 1a and 1b ,each of first and second control levers 130 a and 130 b can have asubstantially L-shaped profile, with first and second grip portions 134a and 134 b extending at a non-zero angle (e.g., between about 50 and 90degrees) away from first and second lever arms 132 a and 132 b,respectively. This angular arrangement allows the operator to engage oneor both of first or second grip portions 134 a or 134 b in a comfortablehand position and pivot first and second control levers 130 a and/or 130b with respect to control system base 120. In some embodiments, firstand second lever arms 132 a and 132 b can be coupled for rotationtogether, whereby pivoting of one of first or second lever arms 132 a or132 b (e.g., by pressing on a respective one of first and second gripportions 134 a or 134 b) causes a corresponding movement of the other.Alternatively, first and second lever arms 132 a and 132 b can beindependently movable with respect to control system base 120 such thatthe operation of either (or both) of first and second lever arms 132 aand 132 b can be moved to control operation of a machine component.

In this regard, to control the operation of the associated machinecomponent (e.g., a self-propel system), first and second control levers130 a and 130 b can be selectively pivoted with respect to controlsystem base 120 between a first angular position (See, e.g., FIG. 1A) atwhich first and second grip portions 134 a and 134 b of first and secondcontrol levers 130 a and 130 b are spaced apart from handle 110 and asecond angular position (See, e.g., FIG. 2b ) at which first and secondgrip portions 134 a and 134 b are drawn against handle 110. Further inthis regard, in some embodiments, when in the second position, at leasta portion of each of first and second grip portions 134 a and 134 b ispositioned within a recess that is formed in an edge of handle 110.

In any configuration, the movement of first and second control levers130 a and 130 b between the first and second angular position caninvolve pivoting the control lever through a limited angular range(e.g., about 35 degrees) such that the movement of first and secondcontrol levers 130 a and 130 b can be comfortably performed by theoperator without letting go of handle 110. In other words, while theoperator is holding handle 110 to steer or otherwise control the workingmachine, the operator can extend his/her thumbs and/or palms backwards ashort distance (e.g., about 71 mm) to grab one or both of first andsecond grip portions 134 a and 134 b while keeping his/her other fingerson handle 110.

Further in this regard, a first speed adjustment actuator 140 a and asecond speed adjustment actuator 140 b can also be provided on controlsystem base 120. First and second speed adjustment actuators 140 a and140 b can be used in combination with first and second control levers130 a and 130 b to further control the operating state of the workingmachine. In the configuration shown in FIGS. 1a and 1b , for example,first and second speed adjustment actuators 140 a and 140 b can comprisepush buttons positioned proximal to first and second control levers 130a and 130 b, respectively. In this arrangement, an operator can easilyreach and depress the push buttons while holding handle 110 and/or firstand second control levers 130 a and 130 b. In particular, first andsecond speed adjustment actuators 140 a and 140 b can be positionedadjacent to a natural thumb position of an operator when the operator ismanipulating first and second control levers 130 a and 130 b. In theconfiguration shown in FIGS. 1a and 1b , for example, such a positioningresults in first speed adjustment actuator 140 a being positioned at ornear a right-most edge of control system base 120 such that it is nearto first control lever 130 a, and second speed adjustment actuator 140 bis positioned at or near a left-most edge of control system base 120such that it is near to second control lever 130 b. Alternatively, firstand second speed adjustment actuators 140 a and 140 b can be provided inany of a variety of other forms, including by not limited to a tactileswitch, a capacitance sensor, a membrane with capacitance sensing, orany other device that is sensitive to touch. In any configuration,variable speed control system 100 can be designed to be easilymanipulated while the operator maintains overall control of the workingmachine.

In operation, where the machine component is a self-propel system for aworking machine, moving first and second control levers 130 a and 130 bto the first angular position can control the machine to be in a firstoperating state, which can be a minimum operating speed or a disengagedstate (i.e., no torque applied). Conversely, upon movement of first andsecond control levers 130 a and 130 b to the second angular position,the machine component can be controlled to be in a second operatingstate. Again, for instance, where the machine component is a self-propelsystem for a working machine, the second operating state can be a fullyengaged or high speed state (i.e., torque applied to the drive systemsuch that the working machine is moved at a selected cruising speed).

Furthermore, those having skill in the art will recognize that first andsecond control levers 130 a and 130 b can additionally be pivoted to anyof a variety of intermediate angular positions to correspondinglyoperate the machine component in one or more partial engagement states(e.g., low- to medium-speed operating states of the self-propel system).In this way, the operator can selectively operate the machine componentat states between the first and second operating states. For example,where the machine component is a self-propel system, positioning firstand second control levers 130 a and 130 b at a selected intermediateposition can control the self-propel system to operate at a speed thatis proportional to the relative angular travel of first and secondcontrol levers 130 a and 130 b between the first and second operatingstates. At any position, however, first and second control levers 130 aand 130 b can be configured to be comfortably held and manipulated bythe operator while maintaining a grip on handle 110.

Furthermore, first and second speed adjustment actuators 140 a and 140 bcan provide additional control over the range of operating statesavailable. In particular, first and second speed adjustment actuators140 a and 140 b can be configured to adjust the value of a parameter ofthe output at the second operating state of the machine component.Again, in the case where the machine component is a self-propel systemfor a working machine, for example, this adjustment allows the maximumoperating speed setting of the self-propel system to be adjusted basedon the preferences of the operator.

In one embodiment, for example, first speed adjustment actuator 140 acan be operable to change the maximum operating speed setting of theself-propel system to have an incrementally higher value, whereas secondspeed adjustment actuator 140 b can be operable change the maximumoperating speed setting of the self-propel system to have adecrementally lower value. In this way, fine adjustments of the maximumoperating speed setting of the working machine can be made withoutdiminishing the operator's ability to control the working machine.

The control inputs from first and second control levers 130 a and 130 band first and second speed adjustment actuators 140 a and 140 b can thenbe communicated to the operation of the working machine. In someembodiments, for example, the working machine can utilize a hybridsystem, such as is illustrated in FIG. 2, in which the working element(e.g., a blade when working machine is a lawn mower) is driven by acombustion engine, generally designated 150, and the self propelleddrive system, generally designated 160, is driven by an electric motor162 that is configured to supply power to one or more wheels 164 of theself-propelled machine at a selected forward ground speed. Drive system160 can be mechanically driven by engine 150 directly, or as shown inFIG. 2, drive system 160 can be electrically driven, and the operationof drive system 160 can be controlled by the operation of a control unit200 (e.g., an electronic control unit (ECU)) that is in communicationwith both engine 150 and variable speed control system 100.

In some aspects, for example, drive system 160 can comprise an electrictransmission, and electric motor 162 can be an electric transmissionmotor that is powered using an electrical actuator or generator 155 orany other type of rotating object (and/or a battery where engine 150 isnot running). In some aspects, electrical actuator or generator 155 canbe coupled and/or mounted onto a crankshaft of engine 150. Electricmotor 162 can be adapted to directly power drive system 160, and drivesystem 160 can be adapted to transfer and/or supply power directly tothe one or more wheels 164 of the self-propelled machine.

As discussed above, variable speed control system 100 can be configuredto be operable by an operator to select a desired ground speed of theself-propelled machine. In particular, the desired ground speed can beselectively chosen by the operator through manipulation of variablespeed control system 100, such as by moving first and second controllevers 130 a and 130 b to any of a range of operating positionscorresponding to one of a predetermined range of desired ground speeds.This operability advantageously allows an operator to choose a groundspeed that best suits the terrain and/or the operator's mobility, amongother factors. Furthermore, the value of the cruising/maximum operatingspeed corresponding to the second angular position of first and secondcontrol levers 130 a and 130 b (i.e., fully-depressed against handle110) can be adjusted up or down by operating first and second speedadjustment actuators 140 a and 140 b. In this way, users who desire tooperate the self-propelled machine at lower speeds do not need tocarefully hold first and second control levers 130 a and 130 b at anunstable intermediate operating position between the fully disengagedand fully engaged states. Rather, such users can simply change themaximum operating speed setting using first and second speed adjustmentactuators 140 a and 140 b, and then move first and second control levers130 a and 130 b to the fully engaged position. This adjustability thusallows the operator to pick a maximum operating speed that can be easilyand consistently achieved without continuously adjusting the position offirst and second control levers 130 a and 130 b.

In this way, the desired ground speed can be selected by the operator,with variable speed control system 100 being configured to transmit theselected desired ground speed, in the form of a signal or pulse, todrive system 160 via control unit 200. For example, variable speedcontrol system 100 can be configured to transmit an electrical signal orpulse (e.g. a control signal) to control unit 200 by way of anelectrical sensor. Variable speed control system 100 can alternativelybe configured to transmit a digital or analog signal to control unit200, while other alternative means of communication can also beutilized. In one aspect, the control signal can communicate the desiredground speed to control unit 200 essentially as a ratio of the desiredground speed compared to the user-defined maximum operating speedsetting (e.g., which can be equal to or less than the system maximumoperating speed setting controlled by first and second speed adjustmentactuators 140 a and 140 b). Under normal operating conditions, controlunit 200 can be configured to control drive system 160 to drive theself-propelled machine at the desired ground speed selected by way ofvariable speed control system 100.

Control unit 200 can correspondingly be configured to receive thecontrol signal from variable speed control system 100. Based at leastpartly on this input, control unit 200 can transmit power to drivesystem 160 via electric motor 162, thereby controlling the transmissionspeed or actual ground speed of the self-propelled machine (e.g., bydriving wheels 164). For example, control unit 200 can be configured sothat the control signal can be transmitted as a signal or pulse to amicrocontroller 210. In one aspect, engine power can be communicated tocontrol unit 200 as alternating current or AC power. Where engine 150 isconfigured to communicate AC power to control unit 200, then controlunit 200 must convert AC power to DC power before reaching electricmotor 162. In one aspect, for example, engine 150 transmits power to arectifier 202 or any other device that converts alternating current (AC)to direct current (DC). After power has been converted from AC power toDC power, a DC power bus 204 can communicate said power in the form of asignal or pulse to a power delivery system, generally designated 206, inorder to control the power supplied to electric motor 162. Powerdelivery system 206 can comprise that of a pulse width modulator or(PWM), a potentiometer, or a rheostat.

In one particular configuration, for example, the control inputs fromfirst and second speed adjustment actuators 140 a and 140 b can becommunicated to and interpreted by control unit 200 in the process shownin FIG. 3. As illustrated in FIG. 3, actuation of first speed adjustmentactuator 140 a can communicate a speed increase signal 302 a to controlunit 200, whereas actuation of second speed adjustment actuator 140 bcan communicate a speed decrease signal 302 b to control unit 200. Aninput reception step 310 can thus include control unit 200 receivingthese inputs, and a comparison step 320 can include identifying whetherone of speed increase signal 302 a or speed decrease signal 302 b isbeing communicated. Specifically, control unit 200 can test whether aspeed increase is requested (e.g., in a speed increase comparison step322 a) or a speed decrease is requested (e.g., in a speed decreasecomparison step 322 b). In some embodiments, a double-input check 312can be performed before comparison step 320 to avoid unnecessary changesin the maximum operating speed setting when both of first and secondspeed adjustment actuators 140 a and 140 b are operated simultaneously.

When only a single input is provided, however, if a speed increase isrequested (i.e., speed increase comparison step 322 a returns a truevalue), control unit 200 can further determine whether increasing themaximum operating speed setting would cause the system to exceed asystem maximum setpoint (e.g., manufacturer-set maximum speed) in amaximum comparison step 330 a. If an increase would not exceed thesystem maximum setpoint, a speed increment step 340 a can increase themaximum operating speed setting. If the maximum operating speed settingalready equals the system maximum setpoint, no change is made.

Alternatively, if a speed decrease is requested (i.e., speed decreasecomparison step 322 b returns a true value), control unit 200 canfurther determine whether decreasing the maximum operating speed settingwould cause the system to fall below an established system minimumsetpoint in a minimum comparison step 330 b. If a decrease would notbring the system below this value, a speed decrement step 340 b candecrease the maximum operating speed setting. If the maximum operatingspeed setting is already at the system minimum setpoint, no change ismade.

The maximum operating speed established by this or by another processcan be displayed to the operator to identify the current setpoint atwhich the working machine is operating and to provide visual feedback tothe operator with respect to how the actuation of first and second speedadjustment actuators 140 a and 140 b affect the maximum operating speedsetting. As shown in FIG. 4, for example, a speed setting indicator 123can be provided on display 122 to graphically indicate the currentsetpoint of the maximum operating speed within the range of possiblevalues (e.g., between a system minimum setpoint and a system maximumsetpoint discussed above). In this regard, speed setting indicator 123can be provided as one of an LED display, and LCD display, an array ofindicator lights, or any of a variety of other display devices known tothose having skill in the art as being able to convey a value and/orrelative speed setting within a given range.

FIGS. 5, 6A, 6B, and 6C show an alternate embodiment that includes amode actuator 542 located on the control system base 120 beneath theengine engagement control 124. FIG. 6A shows the display 122 in astandard mode. Toggling mode actuator 542 allows the user to enter amode selection state 660 of the control unit 200, the display 122 ofwhich is shown in FIG. 6B in standard mode. By depressing the speedactuator 140 a, the user may place the control unit 200 into tractioncontrol mode 670, which is shown in the display 122 in FIG. 6C. The usermay then toggle the mode actuator 542 to return the control unit 200 tostandard mode, as again shown in FIG. 6A. Alternatively, instead ofusing speed actuator 140 a, a separate actuator (not shown) may beprovided for moving between the standard and traction control modes.

By operating in the traction control mode, the control unit 200 cantransmit power to drive system 160 via electric motor 162, therebycontrolling the transmission speed or actual ground speed of theself-propelled machine (e.g., by driving wheels 164), including the rateof acceleration of the self-propelled machine. For example, control unit200 can be configured so that the control signal can be transmitted as asignal or pulse to a microcontroller 210. In one aspect, engine powercan be communicated to control unit 200 as alternating current or ACpower. Where engine 150 is configured to communicate AC power to controlunit 200, then control unit 200 must convert AC power to DC power beforereaching electric motor 162. In one aspect, for example, engine 150transmits power to a rectifier 202 or any other device that convertsalternating current (AC) to direct current (DC). After power has beenconverted from AC power to DC power, a DC power bus 204 can communicatesaid power in the form of a signal or pulse to a power delivery system,generally designated 206, in order to control the power supplied toelectric motor 162. Power delivery system 206 can comprise that of apulse width modulator or (PWM), a potentiometer, or a rheostat.

As discussed those having skill in the art will recognize that first andsecond control levers 130 a and 130 b can additionally be pivoted to anyof a variety of intermediate angular positions to correspondinglyoperate the machine component in one or more partial engagement states(e.g., low- to medium-speed operating states of the self-propel system).However, it is at times difficult for an inexperienced user to operatethe self-propelled machine in this manner. Therefore, it is desirable toprovide a system for controlling acceleration without relying on theuser to manually control acceleration through manual operation of thefirst and second control levers 130 a and 130 b.

FIGS. 7A and 7B are a look-up table 714 and graph of an embodiment ofthe traction control mode 670 where the acceleration rate of the workingelement is a function of the commanded speed of the working element. Asshown in FIG. 7A, the acceleration rate 700 is determined by comparingthe difference of the commanded speed and the actual speed of theworking element as a percentage 710 of the maximum speed. Theacceleration rate 700 is then selected by choosing the correspondingacceleration rate 700 to appropriate speed difference calculation in thelook-up table 714. FIG. 7B shows a comparison of the accelerationprofile in the standard mode 720 and in traction control mode 730. Asshown, the working machine accelerates at a greater rate in standardmode 720 than in traction control mode 730, which may produce wheel spinin certain conditions. The rate of acceleration in traction control mode730 is reduced, which produces a more gradual and smoother tractioncontrol curve on the graph compared with the steeper rate ofacceleration represented by the standard mode 720 curve.

FIG. 8 is a flowchart showing an alternate embodiment that allows theuser to select from a range of acceleration values. The user may selectfrom a large range of acceleration values. In this case, the user wouldselect a scale parameter using the first and second speed controlactuators 140 a and 140 b, as shown in FIG. 5. This scale parameter isdepicted on the bar graph 680 at the bottom of the LED screen 122, asrepresented, for example, in FIG. 6C. This allows the user to adjust theacceleration scale parameter in small increments between and minimum andmaximum value. As an example, the maximum scale factor could be 1.0, theminimum scale factor could be 0.2, and the adjustment increment could beselected from a range of 0.01, giving 80 steps of adjustment, to 0.2,giving 5 steps of adjustment. The LED bar graph 680 shown in FIG. 6Cshows 4 indicators 682, 684, 686, 688, but could have 80 indicators, orin the alternative, can show intermediate adjustment be varying thebrightness of the of the right-most LED 688. For example, if theacceleration setting is adjusted to 90% of the adjustment range, theleft three LEDs 682, 684, 686 would be lit at full brightness, and thefourth LED 688 would be lit at 60% brightness by supplying power with aPWM signal.

In operation of the working machine, the user would first depress thecontrol levers 130 a, 130 b. The control unit 200 calculates, in thefirst step 800, the difference in the commanded speed and actual speedof the working machine. In the second step 810, the control unit 200calculates the acceleration rate from a lookup table 714, such as theone shown in FIG. 7A. Finally, in the third step 820, the accelerationvalue is calculated by the control unit as a function of the value fromthe lookup table 714 multiplied by the scale factor.

In another embodiment, instead of actuating a traction control mode toenter a state where the acceleration of the working machine may bereduced, the user may select an active mode. In active mode, the workingmachine may apply an acceleration profile that accelerates the workingmachine at a quicker rate. In this embodiment, the standard modeconfiguration is the slower mode, whereas an active mode replaces thetraction control mode. Instead of accelerating the working machine moreslowly, the working machine is accelerated more quickly when thealternate mode is selected. In addition to applying a quickeracceleration profile, the control unit may be configured to allow thetop speed of the working machine to be increased. Further in addition,the control unit may be configured such that speed adjustment buttonschange the maximum speed setting more quickly compared to when theworking machine is in standard mode.

In some aspects, the subject matter described herein may be implementedin software in combination with hardware and/or firmware. For example,the subject matter described herein may be implemented in softwareexecuted by a processor (e.g., a hardware-based processor),microprocessor, and/or microcontroller of the electronic control unit.In one exemplary implementation, the subject matter described herein maybe implemented using a non-transitory computer readable medium havingstored thereon computer executable instructions that when executed bythe processor of a computer control the computer to perform steps.Exemplary computer readable media suitable for implementing the subjectmatter described herein include non-transitory devices, such as diskmemory devices, logic devices, logic transistors, chip memory devices,programmable logic devices, such as field programmable gate arrays, andapplication specific integrated circuits. In addition, a computerreadable medium that implements the subject matter described herein maybe located on a single device or computing platform or may bedistributed across multiple devices or multiple computing platforms.

The present subject matter can be embodied in other forms withoutdeparture from the spirit and essential characteristics thereof. Theembodiments described therefore are to be considered in all respects asillustrative and not restrictive. Although the present subject matterhas been described in terms of certain preferred embodiments, otherembodiments that are apparent to those of ordinary skill in the art arealso within the scope of the present subject matter.

What is claimed is:
 1. A variable speed control system for a walk-behindworking machine, the system comprising: a control system base; a controllever selectively movable with respect to the control system basebetween a first operating position and a second operating position; amode actuator positioned on the control system base for toggling betweena standard mode and a selection mode; an adjustment actuator incommunication with a control unit to toggle between a first control modeand a second control mode when the mode actuator is in selection mode;the control unit in communication with the control lever, the adjustmentactuator, the mode actuator, and a machine component, wherein thecontrol unit selectively controls the operation of the machine componentbetween a minimum operating speed and a variable maximum operatingspeed; wherein the control lever communicates with the control unit tocontrol the machine component to operate at the minimum operating speedwhen the control lever is in the first operating position and to controlthe machine component to operate at the variable maximum operating speedwhen the control lever is in the second operating position; and whereinthe control unit applies a first acceleration profile to accelerate fromthe minimum operating speed to the variable maximum operating speed whenin the first control mode, and wherein the control unit applies a secondacceleration profile to accelerate from the minimum operating speed tothe variable maximum operating speed when in the second control mode. 2.The variable speed control system of claim 1, wherein the machinecomponent comprises a variable transmission for a self-propel system ofthe working machine; wherein the minimum operating speed comprises adisengaged state of the machine component; and wherein the variablemaximum operating speed comprises operation of the self-propel system ata cruising speed defined by the variable value.
 3. The variable speedcontrol system of claim 1, wherein the adjustment actuator comprises, aspeed adjustment actuator positioned on the control system base incommunication with a control unit to toggle between the first controlmode and the second control mode when the mode actuator is in controlselection mode.
 4. The variable speed control system of claim 3 whereinthe speed adjustment actuator comprise an apparatus selected from thegroup consisting of a push button, a tactile switch, a capacitancesensor, and a membrane with capacitance sensing.
 5. The variable speedcontrol system of claim 1, wherein the control unit selectively controlsthe operation by controlling a power delivery system connected to themachine component.
 6. The variable speed control system of claim 1wherein: the first acceleration profile comprises a first lookup tablestored in a memory of the control unit that assigns acceleration ratesas a first function of the variable maximum operating speed; and thesecond acceleration profile comprises a second lookup table stored inthe memory of the control unit that assigns acceleration rates as asecond function of the variable maximum operating speed.
 7. The variablespeed control system of claim 1 wherein: the first acceleration profilecomprises a first lookup table stored in a memory of the control unitthat assigns acceleration rates as a first function of a differencebetween the variable maximum operating speed and a current speed of thewalk-behind working machine; and the second acceleration profilecomprises a second lookup table stored in the memory of the control unitthat assigns acceleration rates as a second function of a differencebetween the variable maximum operating speed and a current speed of thewalk-behind working machine.
 8. A variable speed control system for awalk-behind working machine, the system comprising: a control systembase; a control lever selectively movable with respect to the controlsystem base between a first operating position and a second operatingposition; a mode actuator positioned on the control system base fortoggling between a standard mode and a selection mode; an adjustmentactuator in communication with a control unit to toggle between a firstcontrol mode and a second control mode when the mode actuator is inselection mode; the control unit in communication with the controllever, the adjustment actuator, the mode actuator, and a machinecomponent, wherein the control unit selectively controls the operationof the machine component between a minimum operating speed and avariable maximum operating speed; wherein the control lever communicateswith the control unit to control the machine component to operate at theminimum operating speed when the control lever is in the first operatingposition and to control the machine component to operate at the variablemaximum operating speed when the control lever is in the secondoperating position; and wherein the control unit applies theacceleration scale factor to control acceleration from the minimumoperating speed to the variable maximum operating speed.
 9. The variablespeed control system of claim 8, wherein the machine component comprisesa variable transmission for a self-propel system of the working machine;wherein the minimum operating speed comprises a disengaged state of themachine component; and wherein the variable maximum operating speedcomprises operation of the self-propel system at a cruising speeddefined by the variable value.
 10. The variable speed control system ofclaim 8, wherein the adjustment actuator comprises, a speed adjustmentactuator positioned on the control system base in communication with acontrol unit to toggle between the first control mode and the secondcontrol mode when the mode actuator is in control selection mode. 11.The variable speed control system of claim 10, wherein the speedadjustment actuator comprises a device selected from the groupconsisting of a push button, a tactile switch, a capacitance sensor, anda membrane with capacitance sensing.
 12. The variable speed controlsystem of claim 8, wherein the control unit selectively controls theoperation by controlling a power delivery system connected to themachine component.
 13. A method for varying a speed of a walk-behindworking machine, the method comprising: actuating a mode actuatorpositioned on a control system base to select a selection mode;actuating an adjustment actuator positioned on the control system baseto select a mode for controlling a rate of acceleration of saidwalk-behind working machine from a minimum operating speed to a variablemaximum operating speed; moving a control lever with respect to acontrol system base between a first operating position and a secondoperating position; without releasing the control lever, selectivelyactuating the adjustment actuator; wherein moving the control lever tothe first operating position controls a machine component to operate atthe minimum operating speed; wherein moving the control lever to thesecond operating position controls the machine component to operate atthe variable maximum operating speed; and wherein actuating theadjustment actuator increases the value of the variable maximumoperating speed.
 14. The method of claim 13, wherein the machinecomponent comprises a variable transmission for a self-propel system ofthe working machine; wherein controlling the machine component tooperate at the minimum operating speed comprises operating the machinecomponent in a disengaged state; and wherein controlling the machinecomponent to operate at the variable maximum operating speed comprisesoperating the self-propel system at a cruising speed defined by thevalue of the variable maximum operating speed.
 15. The method of claim13, wherein moving the control lever with respect to the control systembase comprises pivoting a lever arm of the control lever, the lever armbeing pivotably coupled to the control system base; wherein moving thecontrol lever to the first operating position comprises pivoting thelever arm to a first angular position relative to the control systembase; and wherein moving the control lever to the second operatingposition comprises pivoting the lever arm to a second angular positionrelative to the control system base.
 16. The method of claim 13, whereinthe adjustment actuator comprises, a speed adjustment actuatorpositioned on the control system base in communication with a controlunit to toggle between the first control mode and the second controlmode when the mode actuator is in control selection mode.
 17. The methodof claim 16, wherein actuating the speed adjustment actuator comprisespushing a push button or touching one of a tactile switch, a capacitancesensor, or a membrane with capacitance sensing.
 18. The method of claim13, wherein actuating the adjustment actuator comprises comparing thevalue of the variable maximum operating speed to a system maximumsetpoint; and increasing the value of the variable maximum operatingspeed by an increment if the value of the variable maximum operatingspeed is less than the system maximum setpoint.
 19. The method of claim13, wherein moving the control lever with respect to a control systembase between a first operating position and a second operating positionvaries an output of a power delivery system connected to the machinecomponent.